This invention relates to reciprocating engines employing oil-cooled pistons.
Many engines in use today employ oil-cooled pistons for known reasons. In some such pistons, there is an annular passage in proximity to the ring-receiving grooves having a downwardly open port. A nozzle is located below the cylinder receiving the piston and in alignment with the inlet port for spraying oil upwardly into the piston to be received in the annular passage and cool the piston in the vicinity of the rings. Consequently, the rings are cooled with the result that a thicker oil film is developed at the interface between the rings and the cylinder wall providing better lubrication qualities.
Others merely direct a spray of oil to the interior of the piston crown for cooling purposes.
In the case of the former type, precise alignment of the nozzle with the inlet port is required since the nozzle will be stationary while the piston will be moving and it is desired to direct oil to the annular coolant passage at all times. In the case of the latter, wrist pin receiving bosses as well as the wrist pin and, when the piston is moved upwardly within the cylinder and away from the spray, the connecting rod interfere with the spray pattern and can prevent, at various times in the cycle, the coolant from reaching all interior surface parts of the piston, resulting in localized hot spots which can lead to cracking of the piston.
In many cases, because of the precise alignment of the sprays with the piston parts, servicing is difficult, often requiring disassembly of engine parts such as the crank shaft, bearing, etc.